1. Field of the Invention
The present invention relates to target tracking and apparatus, and particularly to a method and apparatus for controlling a picture-taking device to track a moving object by utilizing a calculation of a correlation between a correlation area extracted from a former image and a checking area extracted from a current area.
2. Description of the Prior Art
A target tracking technique is applied to various fields: for example, a military missile, an aircraft, and a video conference system or a video phone. Generally, a tracking method to track a target include a center point tracking method and a correlation tracking method.
The center point tracking method is, as shown in FIG. 2a, a method where a moving object is separated from a background and then a center point of the extracted object serves as a reference in tracking. In this method, in order to separate the object from a background by utilizing a threshold, the background and the object are digitized. The method has good tracking stability and is little influenced by noises when an image is simple so as to easily be partitioned and the method is relatively little restricted by the velocity of a target, but when the condition is contrary to these conditions, it has bad tracking stability and is much influenced by noises.
The correlation tracking method is, as shown in FIG. 2b, a method that defines a proper size of a correlation area B in a former image on the basis of a location of a target or a moving object, and then calculates the correlation between the correlation area B and a checking area in a current image to estimate a movement of the object into an area B' whose correlation is highest. Without digitizing an image, the correlation tracking method gives good tracking stability even in a tracking of a relatively complex image because it performs a direct calculation of correlation by utilizing luminosity information of a currently input image. However, the method has such defects that it has large data to be calculated because the correlation calculation between the correlation area and the checking area should be performed throughout both areas.